+
+ /*
+ * Finally, pull caller's reference if the STA is pinned by the
+ * task that is adding the debugfs entries. In that case, we
+ * leave the STA "to be freed".
+ *
+ * The rules are not trivial, but not too complex either:
+ * (1) pin_status is only modified under the sta_lock
+ * (2) STAs may only be pinned under the RTNL so that
+ * sta_info_flush() is guaranteed to actually destroy
+ * all STAs that are active for a given interface, this
+ * is required for correctness because otherwise we
+ * could notify a driver that an interface is going
+ * away and only after that (!) notify it about a STA
+ * on that interface going away.
+ * (3) sta_info_debugfs_add_work() will set the status
+ * to PINNED when it found an item that needs a new
+ * debugfs directory created. In that case, that item
+ * must not be freed although all *RCU* users are done
+ * with it. Hence, we tell the caller of _unlink()
+ * that the item is already gone (as can happen when
+ * two tasks try to unlink/destroy at the same time)
+ * (4) We set the pin_status to DESTROY here when we
+ * find such an item.
+ * (5) sta_info_debugfs_add_work() will reset the pin_status
+ * from PINNED to NORMAL when it is done with the item,
+ * but will check for DESTROY before resetting it in
+ * which case it will free the item.
+ */
+ if ((*sta)->pin_status == STA_INFO_PIN_STAT_PINNED) {
+ (*sta)->pin_status = STA_INFO_PIN_STAT_DESTROY;
+ *sta = NULL;
+ return;
+ }